/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * A delegating wrapper around a {@link ListenableFuture} that adds support for the
 * {@link #checkedGet()} and {@link #checkedGet(long, TimeUnit)} methods.
 *
 * @author Sven Mawson
 * @since 1.0
 * @deprecated {@link CheckedFuture} cannot properly support the chained operations that are the
 *             primary goal of {@link ListenableFuture}. {@code CheckedFuture} also encourages users
 *             to rethrow exceptions from one thread in another thread, producing misleading stack
 *             traces. Additionally, it has a surprising policy about which exceptions to map and
 *             which to leave untouched. Guava users who want a {@code CheckedFuture} can fork the
 *             classes for their own use, possibly specializing them to the particular exception
 *             type they use. We recommend that most people use {@code ListenableFuture} and perform
 *             any exception wrapping themselves. This class is scheduled for removal from Guava in
 *             February 2018.
 */
@Beta
@Deprecated
@GwtIncompatible
public abstract class AbstractCheckedFuture<V, X extends Exception>
        extends ForwardingListenableFuture.SimpleForwardingListenableFuture<V> implements CheckedFuture<V, X> {
    /**
     * Constructs an {@code AbstractCheckedFuture} that wraps a delegate.
     */
    protected AbstractCheckedFuture(ListenableFuture<V> delegate) {
        super(delegate);
    }

    /**
     * Translates from an {@link InterruptedException}, {@link CancellationException} or
     * {@link ExecutionException} thrown by {@code get} to an exception of type {@code X} to be
     * thrown by {@code checkedGet}. Subclasses must implement this method.
     *
     * <p>
     * If {@code e} is an {@code InterruptedException}, the calling {@code checkedGet} method has
     * already restored the interrupt after catching the exception. If an implementation of
     * {@link #mapException(Exception)} wishes to swallow the interrupt, it can do so by calling
     * {@link Thread#interrupted()}.
     *
     * <p>
     * Subclasses may choose to throw, rather than return, a subclass of {@code RuntimeException} to
     * allow creating a CheckedFuture that throws both checked and unchecked exceptions.
     */
    // We might like @ForOverride here, but some subclasses invoke this from their get() methods.
    protected abstract X mapException(Exception e);

    /**
     * {@inheritDoc}
     *
     * <p>
     * This implementation calls {@link #get()} and maps that method's standard exceptions to
     * instances of type {@code X} using {@link #mapException}.
     *
     * <p>
     * In addition, if {@code get} throws an {@link InterruptedException}, this implementation will
     * set the current thread's interrupt status before calling {@code mapException}.
     *
     * @throws X if {@link #get()} throws an {@link InterruptedException},
     *         {@link CancellationException}, or {@link ExecutionException}
     */
    @CanIgnoreReturnValue
    @Override
    public V checkedGet() throws X {
        try {
            return get();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            throw mapException(e);
        } catch (CancellationException e) {
            throw mapException(e);
        } catch (ExecutionException e) {
            throw mapException(e);
        }
    }

    /**
     * {@inheritDoc}
     *
     * <p>
     * This implementation calls {@link #get(long, TimeUnit)} and maps that method's standard
     * exceptions (excluding {@link TimeoutException}, which is propagated) to instances of type
     * {@code X} using {@link #mapException}.
     *
     * <p>
     * In addition, if {@code get} throws an {@link InterruptedException}, this implementation will
     * set the current thread's interrupt status before calling {@code mapException}.
     *
     * @throws X if {@link #get()} throws an {@link InterruptedException},
     *         {@link CancellationException}, or {@link ExecutionException}
     */
    @CanIgnoreReturnValue
    @Override
    public V checkedGet(long timeout, TimeUnit unit) throws TimeoutException, X {
        try {
            return get(timeout, unit);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            throw mapException(e);
        } catch (CancellationException e) {
            throw mapException(e);
        } catch (ExecutionException e) {
            throw mapException(e);
        }
    }
}
